Re: [PATCH] BaseTools/tools_def: use separate PP definition for DTC

["Gao, Liming" <liming.gao@intel.com>]

Reviewed-by: Liming Gao <liming.gao@intel.com>

> -----Original Message-----
> From: Leif Lindholm [mailto:leif.lindholm@linaro.org]
> Sent: Wednesday, February 28, 2018 4:01 AM
> To: Ard Biesheuvel <ard.biesheuvel@linaro.org>
> Cc: edk2-devel@lists.01.org; Gao, Liming <liming.gao@intel.com>; Zhu, Yonghong <yonghong.zhu@intel.com>
> Subject: Re: [PATCH] BaseTools/tools_def: use separate PP definition for DTC
> 
> On Tue, Feb 27, 2018 at 07:02:06PM +0000, Ard Biesheuvel wrote:
> > On 27 February 2018 at 18:58, Leif Lindholm <leif.lindholm@linaro.org> wrote:
> > > On Tue, Feb 27, 2018 at 06:36:08PM +0000, Ard Biesheuvel wrote:
> > >> On 27 February 2018 at 18:33, Leif Lindholm <leif.lindholm@linaro.org> wrote:
> > >> > On Tue, Feb 27, 2018 at 05:51:32PM +0000, Ard Biesheuvel wrote:
> > >> >> Clang's preprocessor behaves differently from GCC's, and produces
> > >> >> intermediate device tree source that still contains #pragma pack()
> > >> >> and other directives that the device tree compiler chokes on.
> > >> >>
> > >> >> For assembling device tree sources, it matters very little which
> > >> >> preprocessor is being used, so let's just use GNU CPP explicitly.
> > >> >
> > >> > Ah, right, same fundamental issue as
> > >> > 5b8766bb92debfa7b2f45a4a6d683b4227360d66.
> > >>
> > >> Yes, and I fail to see why changing just those two files makes a
> > >> meaningful difference.
> > >
> > > Probably because Secure96Dxe.inf has a lot more [Packages] and
> > > [LibraryClasses] dependencies than DeveloperBox.inf.
> > >
> > > This patch would undoubtedly also have resolved that issue.
> > > (As would clang preprocessor not throwing out C syntax when explicitly
> > > asked to provide asm.)
> > >
> > >> > However, this time triggered by autogen seemingly forcing inclusion of
> > >> > lots of central header files that are not even used, like
> > >> > MdePkg/Include/IndustryStandard/Bluetooth.h
> > >> > MdePkg/Include/IndustryStandard/Acpi10.h
> > >> > and so on.
> > >> >
> > >> > Is there any way to suppress these implicit includes from .dts
> > >> > processing?
> > >>
> > >> There is 'Trim', which can filter #include'd content, but using that
> > >> also robs us of the ability to #include .dtsi files, which was kind of
> > >> the point of using the preprocessor in the first place.
> > >
> > > Yeah, that'd definitely be missing the point slightly.
> > >
> > > I was thinking more along the lines of either excluding the autogen
> > > bits from the preprocessing or using a separate .inf for the .dts.
> > >
> >
> > We need the AutoGen.h bits for the fixed PCD values, which was the
> > other reason for using the preprocessor in the first place.
> 
> Yeah, I was afraid of that.
> 
> > Separate .inf would mean registering file GUIDs in the package .DEC,
> > so that the driver can find the binary image at runtime, which is what
> > I was trying to get away from by pulling it into the driver,
> > especially because we are dealing with overlay DT snippets, of which
> > there may be many, rather than a single DT (with a well known file
> > GUID) for the entire platform.
> >
> > > If neither of those feels practical, the proposed patch is fine.
> > > It just feels a little bit clunky.
> >
> > Yeah, I don't see any unclunky solutions, unfortunately.
> 
> Fair enough.
> Reviewed-by: Leif Lindholm <leif.lindholm@linaro.org>